Pesticides have already produced catastrophic impacts on many species of birds. Both the insect-eaters and birds of prey, such as the osprey and the American eagle, appear threatened with extinction by the effects of DDT and other long-lived insecticides. While the effects are heavily concentrated in the countries that use them most, particularly the United States, the nondegrad-able nature of these pesticides and their gradual worldwide dispersion means that their damaging effects will continue to spread and be greatly accelerated if other countries use them in anything like the quantities used in the United States. Limiting or even stopping the use of this type of insecticide seems imperative in the not-too-distant future; the impact on less developed countries may be serious, particularly as it may affect control of certain insect-borne diseases.
Other drastic impacts on the environment are to be expected from both increasing populations and adoption of new technologies. Primitive agriculture is notorious for its destruction of the soil through overgrazing, single-crop cultivation, and burning of vegetative cover. Larger populations intensify these problems, but new problems often result from the introduction of new technologies and new crops. Fertilizers may produce problems of soil salinity or eutrophy of watercourses and lakes. New plant species may be more vulnerable to disease or drought.
All the major sources of change—larger population, increased urbanization, new technologies, and higher levels of living—tend to create scarcities of the "new" resources of fresh air, pure water, and open space. New in the sense that they have not been allocated in the market place, have not borne a price, and therefore have not been subject to care and economizing, these resources pertain to "quality of the environment." Generally taken for granted, they are only gradually coming into the realm of measurement, analysis, and public policy.
Air quality has diminished rapidly as a result of urbanization, higher living standards, and modern technology. Urbanization, which is increasing much more rapidly than total population, is correlated with higher levels of per capita production (Figure 2) which in turn is closely correlated with higher fuel use (Figure 3). Mineral fuels which provide heat, electricity, and transportation have been the principal detractors from air quality. In some American cities the motor car is charged with producing as much as 80 percent of the total air pollution. In other areas, the principal polluters are ore smelters, blast furnaces, pulp mills, or steam plants for generating electricity. A quick index of overall air pollution is the consumption of mineral fuels, although the degree of impact depends on specific local conditions, including theof raising difficulties with "quality."s 143-148), although in most cases they appeared to be incomplete.